1. Field of the Invention
The present invention relates to a highly reliable two-terminal nonlinear device used as a switching device where the sharpness of the voltage-current characteristic is sufficiently large and change of the voltage-current characteristic is small, a method for manufacturing the two-terminal nonlinear device, and a liquid-crystal display panel having high image quality without display irregularity or sticking and with high contrast that uses the two-terminal nonlinear device.
2. Description of Related Art
In an active matrix-type liquid-crystal display device, liquid crystal is filled between an active-matrix substrate which forms a matrix array by disposing a switching device for each pixel area and an opposing substrate in which a color filter is disposed, for example. Alignment of the liquid crystal for each pixel area is controlled to display desired image information. In general, a three-terminal device such as a thin film transistor (TFT) or a two-terminal device such as metal/insulating material/metal (MIM) nonlinear devices is used as a switching device. A two-terminal device used as a switching device is more advantageous than a three-terminal device since two-terminal devices are free of cross-over shorting and can be manufactured by a simpler process.
Japanese Patent Laid-Open Publication No. Sho 63-50081 discloses a technique for improving nonlinearity of a MIM nonlinear device. In this technique, a tantalum film is subjected to anodic oxidation and heat-treated at a temperature of 400.degree.-600.degree. C., to improve the nonlinearity, particularly, the sharpness of the voltage-current characteristic. However, sufficient nonlinearity has not been obtained even by this technique.